1. Field of the Invention
The present invention relates to a grease composition and, more specifically, to a grease composition used in a constant velocity joint and the like.
2. Related Background Art
Constant velocity joints are joints for a shaft transmitting a driving force from a transmission of a car to its tires, for example. Their types include fixed type constant velocity joints such as Barfield joint, Rzeppa joint, and undercutting free joint; slide type constant velocity joints such as double-offset joint, tripod joint, and cross-groove joint; and the like.
For achieving a longer life in these constant velocity joints, the selection of grease is very important. Therefore, conventional constant velocity joints have widely employed a grease in which an additive such as a lead compound is compounded with a base grease comprising a lubricant base oil and lithium soap or urea type thickener, thereby improving such performances as anti-flaking, anti-seizure, anti-wear, low friction, and the like.